TURAM EM testing over the Elura orebody

Abstract

Two Turam surveys with a frequency range between 35 and 660 Hz were conducted over the Elura orebody in 1977 and 1979. The first survey using a 700 m ´ 300 m loop centred on line 20100 E, produced a definable anomaly over the orebody but the data were generally noisy. Data from the second survey using an 800 m ´ 400 m loop centred on line 50800 N were less noisy. Anomalies were recorded on two lines over the orebody. No significant anomalies were recorded over two other lines, one on the edge and the other off the orebody. Over the limited extent that data could be collected owing to poor signal strengths (some 600 m from the leading edge of the large loops), it is possible to define orebody anomalies in a frequency range up to 105 Hz and possibly to 220 Hz. The problem with this exploration technique is that loop positioning is critical and that both geological noise (variations in the overburden depth and resistivity) and telluric noise degrade the data, making the Turam method at these frequencies unsuitable for exploration in the Cobar type environment. Analogue and digital modelling results are shown in an attempt to clarify and define the Turam anomaly expected over the Elura orebody.